Intrinsic Specific Activity Enhancement for Bifunctional Electrocatalytic Activity toward Oxygen and Hydrogen Evolution Reactions via Structural Modification of Nickel Organophosphonates.

A comprehensive knowledge of the structure-activity relationship of the framework material is decisive to develop efficient multifunctional electrocatalysts. In this regard, two different metal organophosphonate compounds, [Ni(Hhedp)]·4HO () and [Ni(Hhedp)(CHN)]·6HO () have been isolated through one-pot hydrothermal strategy by using Hhedp (1-hydroxyethane 1,1-diphosphonic acid) and N-donor auxiliary ligand (pyrazine; CHN). The structures of synthesized materials have been established through single-crystal X-ray diffraction studies, which confirm that compound formed a one-dimensional molecular chain structure, while compound exhibited a three-dimensional extended structure. Further, the crystalline materials have participated as efficient electrocatalysts for the oxygen evolution and hydrogen evolution reactions (OER and HER) as compared to the state-of-the-art electrocatalyst RuO. The electrocatalytic OER and HER performances show that compound displayed better electrocatalytic performances toward OER (η = 305 mV) and HER (η = 230 mV) in alkaline (1 M KOH) and acidic (0.5 M HSO) media, respectively. Substantially, the specific activity has been assessed in order to measure the inherent electrocatalytic activity of the title electrocatalyst, which displays an enrichment of fourfold higher activity of compound (0.64 mA/cm) than compound (0.16 mA/cm) for the OER experiments. Remarkably, inclusion of an auxiliary pyrazine ligand into the metal organophosphonate structure (compound ) not only offers higher dimensionality along with significant enhancement of the overall bifunctional electrocatalytic performances but also improves the long-term stability, which is noteworthy for the family of hybrid framework materials.